This invention relates to an energy absorbing safety barrier.
A number of approaches have been taken to protect vehicle drivers, and other vehicles, from accidental impacts against bridge abutments and other fixtures. Sand-filled barrels, for example, can be placed in front of such obstacles to absorb the energy of a vehicle upon impact over a greater distance than if the obstacle were directly struck. Doing so reduces the maximum deceleration of the vehicle, and thus improves the chances for surviving such an accident. Old vehicle tires have been used as barrier for years at auto races, and along piers.
Pneumatic energy absorbers have also been proposed. They tend, however, to be more expensive than the simpler solutions, and they create a new problem of rebound: a pneumatic barrier can act as a spring, redirecting a vehicle back into traffic in a direction opposed to the general flow of traffic. Rebounds of this type are potentially fatal.
Prior inventors have addressed the problem of absorbing the tremendous impacts which vehicles traveling at high speed can produce. U.S. Pat. No. 4,674,911 describes a cushion made of accordion-type members, and has valves to control air release upon impact. U.S. Pat. No. 4,848,853 discloses a highway impact device made of tires stacked vertically.
The need remains, however, for an device which can absorb great vehicle impacts, minimizes rebound, and is also inexpensive to construct.
An object of the invention is to provide a device which can safely arrest vehicles in high-speed impacts.
A related object is to prevent vehicle rebound after impact.
A further object is to provide a device which can be constructed largely from materials which are free or at least very inexpensive.
These and other objects are attained by an energy absorbing safety barrier formed from pneumatic tires, as described below.
According to the present invention, tires are formed into horizontal stacks, bound together permanently at the sidewalls. Plates at either end of the stack form sealed chambers, normally at atmospheric pressure. When the stack is struck by a vehicle, it absorbs energy primarily through the mechanism of air compression within the stack, as in an air bag, rather than from the resiliency of the tires themselves. Rebound is minimized by allowing air to escape through vent valves which substantially close as the stack expands following an impact.